Reactance tube timing modulator



Oct. 14; 1947. R, w, CLARK 2,423,931

REACTANCE TUBE TIMING MODULATOR Filed May 26, 1943 INVENTOR ATTORNEY Patented Oct. 14, 1!?47 Robert W; Clark,- Teaneck, N.- J., assignor to Radio- Corporation of America; a coi-pofaition of D'ela# ware terns tdbe used at high-frequencies."

li ifsystejms of; this type". known heretofore the phaseqquadrature' relation between the reactance tube cut'puti'electrode voltage and the 'reactance' V tuhef 'coritrol electrode voltagelisj obtained by,

luinpjedj capacities"; inductan'cesfand resistances. AttirehighenfrequencieS theiuse of these lumped constants I is not 'p'artici ila rly feasible 1 because of distributed capacities of inductances and resistances and inductance Ofleadssuch asthose m eap au sa atween tube electrodes and circuitelement'si 1' object oflmy invention isto provide a new andjimproved' reactance ma um wherein the v phase 'hi'fting, networ l is"compri'sed of re'a 'ctaric'e Y o"fs 11 1al1. distributed capacity, andto provide a new and improved modulation j system j using said, inip'r'ov'ed"tubejreactance. In my improved system the phase quadrature 'ent is obtained by meansof [a section of v Q smisfsilon line' fhich per selserves as the phase shifting network s 'well" as the connection.

In describing m'y'inyention in detail, reference will beniadetc the attached drawings whereini;

Figs. l and'jZe'ach show the essential features! of twoi'embodi'rnents'of my v'ariableftube reactance and the tuned ci'rcu'ilt to which it iscouple'd to produce 'the i'eactiveieffect and the connections forcontrolling the said reactive effect tolmodulate. the timing-moi wave energy-in the 'tuned circuit. Iriitheembodimentillustrated in Fig. litube I0 in coiijunction withialsection of coaxial line" I2- forins a regenerative oscillation generator of the grounded ma type; The-anode I4 as stated is at ground radio" frequency potential and the grid I 6 at ajradioqfrequencypotential above ground which radio frequency potential is 180 out of phase with respect to the'pha'se of'the, anode radio frequency potential. T The cathode I8, is maintained a. radio frequencygpotentiai above ground and. the phases of the potentials on the grid and anode-"are ahoiit opposed." The inductance 2. 0.92 appropriate value io r; the frequency in-, vol ed serves tomaintain the, cathode aboye t s d"- d q'i sqaeermeetin In this form of oscillation generator the inner conductor of the coaxial line I2 has voltage nodes at both ends, its effective length being the equiva- 2 (sit i (c1. no 11115)- lent ofgon e-halipf the length of thewave-gener- I ated The'aIiodeZB of reactance tube 24 is con; nejcted too'ne endof'theinner conductor of the oscillator tank cir' cuit line I2. This holds the anode atia highirequency voltage of a first phase dio f equenc ene y n e in s kuni 2 b ea s offa sectionofftransmissioriline 21. Theilength' f of 'th'islin'eiZL is such thatthephase of the radio frequency. voltage at grid1 26 .is, substantially in quadrfature with respect to the voltage on anode; w tu 2 hu i eb rrent drawn bytubszn is about in phase quadrature with the, voltage onl anode rege erate simulates a reactanceacross! e fi d o t e-mina t t k u l ihe br loop, 25, and'is fedZto-gridQZG of tube n rol i t requ n 0 O i i ond nser. is a o. f ue c cQup s.-. n denser which couples the. oscillator grid I6 to the member of line I2 operating at high radio irequency potentiaL- This condenser I also prevents plategdirect current potential from reaching the, gridiI5.. Condenser 9 isa radio frequencycQ -s,

pling j and direct current blocking condenser con.-

meeting: the cathodel's .to a point on theesame. I I' is thevgrid bias resistance Iiisfla radio frequency. bypass condenser connecting the. anode I4 of tubexlll to ground. 20 is an induct member'ofline I2. connecting thegrid. I6 to the cathode I8.

ance', appropriate'f'or the frequency usedrconnecting the cathode I8'to ground to maintain the cathode above ground alternating current 'potenij tial. I3 is' a' radio frequency bypass condenser" connecting the second grid of the re'actance tube Mtto ground, I1 is a radio frequency couplingf condenser couplingthe grid 26 to the inner conductor'of 1irie 21, I9 is a modulation coupling condenser forf e eding modulatinggpotentials tol theg'rid ofthe' modulator tube28 and 2| is a ra-f dio frequency chokebetween the anode 23 of .tu'bej 1B and egd rect. c rent u c -i than M4 since it is dimensioned byadjustment to compensate for tubet-ransit time which is too be considered :at high; frequencies and also adjustedto compensate vfor the length; of connecting leads such as-bietween theanode 23 and the line I2 and between the grid 2.6 and line 21.

Modulation may beapplied to any elementof tube shown; in this case as being applied to j grid 26;,throughmodu1ator tube 28.: The cur-v rent-through tube24 is a determinating charaQ- teristic of the frequency of oscillation and the current through this tube is regulated by the modulating signal. In this manner the modulatq ing signal will govern the frequency of the oscillations generated.

The modulated carrier may be derived from a loop coupled to the inner conductor of line 12 or by coupling to an oscillator tube electrode.

While in Fig. 1 the pickup loop is shown at one end of the oscillator tank circuit I2, I may locate this pickup loop anywhere along the oscillator tank circuit. A corresponding adjustment in the length of line 2'! must then be made in order that the voltage on grid 26 will be in phase quadrature with the voltage on anode 23,

In Fig. 2 is shown a modification of the circuit of Fig. 1. In Fig. 2, tube 39 in cooperation with the section of coaxial line 3| forms an oscillator of the grounded anode variety wherein the electrode 32 of tube 39 acts as the anode of the oscillator. In this oscillator the grid 40 is at a high radio frequency potential with respect to ground and is coupled by condenser 36 to the inner member of coaxial line 3! at a point where the generated voltage is 180 out of phase with respect to the voltage on the electrode 32 serving as the oscillator anode. The cathode 33 of tube is at an intermediate radio frequency potential being held above ground by the inductance 34. Condenser 35 is a radio frequency bypass condenser coupling the oscillator anode 32 to the grounded member of line 3|. This condenser 35 also serves as a direct current blocking condenser. Condenser 36 is the grid radio frequency coupling condenser coupling the grid All to the inner member of line 3| and resistor 31 is the grid resistor connecting grid to ground and thence to the cathode 33.

The reactance tube 38 has its anode 39 connected to grid 40 by means of the radio frequency coupling condenser 4|, so that the radio frequency voltage on the anode 39 is the same as that on grid and is of a first phase. Inductance 42 presents a high impedance to the radio frequencies, keeping anode 39 and grid 40 at high radio frequency potential above ground, Anode 43 of tube 39 being electron coupled to the generating electrodes is connected to grid 44 of tube 38 by a section of transmission line 45. The length of this line is such that the voltage on grid 44 is about in phase quadrature with respect to said first phase of the voltage on the anode 39 of tube 38. then be about in phase quadrature with the voltage on its anode 39 and on grid 4!], so that tube 38 will appear as a reactance between grid 49 and ground, This effectivel connects a reactance across the grid end of the oscillator tank circuit formed by line 3! and this eiTective reactance is a determining component of the frequency of oscillations. The plate current of tube 38 is varied in accordance with a modulating signal applied through tube 45 to grid 44 of tube 38, so the frequenc of oscillation will vary in accordance with the modulating signal. The modulated output may be taken from a loop coupled to the inner conductor of line 3!.

In this arrangement, as in Fig. 1, the line 45 The current taken by tube 38 will 4 quadrature with the plate voltage the grid voltage may be more or less than 90 out of phase with respect to the platecurrent. Thus at ultrahigh frequency line 21, or 45 may be considerably less than M4.

' In the system disclosed, I have shown in a conventional manner a triode generator at Ill and two grid tubes at 24, 30 and 38, In practice I V may use tubes of any type suitable for the purl0 pose.

I claim:

1. In a tube reactance, a two-conductor transmission line wherein high frequency waves are developed, a tube having an electron receiving electrode coupled by a path of low impedance to said high frequency waves, to one of the conductors of said line, whereby voltage of a first phase is set up on said electron receiving electrode, said tube having an electron flow control electrode and an electron source electrode, a substantially direct coupling between said electron source electrode and the other conductor of said line to put the impedance between the electron receiving electrode and the electron source electrode in shunt to the conductors of said line, a second line of a' length substantially equal to M4, where A is the wavelength of the high fre-- quency waves, a tube coupling between one end of said last named line and said first line to feed voltage to said second line, and a coupling between the other end of said second line and the electron flow control electrode of said tube, to feed to said electron fiow control electrode a voltage the phase of which is substantiall in quadrature with the phase of said voltage of said first phase, whereby a reactive efiect is produced in said tube and reflected into said first line.

2. In a reactance tube timing modulation system, a two-conductor transmission line wherein high frequency waves are developed, a tube having an electron receiving electrode coupled substantially directly to one end of one conductor of said line, whereby voltage of a first phase appears on said electron receiving electrode, said tube having an electron fiow control electrode and an electron source electrode, a coupling between said electron source electrode and the other conductor of said line to put the impedance between the electron receiving electrode and the electron source electrode in shunt to the conductors of said line, a transmission line of a length substantially equal to M4, where x is the wavelength of the high frequency waves, an electronic coupling between one end of said last named line and said first line, a coupling between the other end of said second line and the electron flow control electrode of said tube to feed to said flow controlelectrode a voltage the phase of which is substantially in phase quadrature with respect to they phase of said voltage of said first phase and connections for controlling the transconductance of said tube in accordance with signals,

ROBERT W. CLARK.

REFERENCES CITED The following references are of record in the file of this patent:

' UNITED STATES PATENTS Number Name Date 2,280,026 Brown Apr, 14, 1942 2,304,377 Roberts Dec. 8, 1942 

